Press 'I' (4 inventory) find alchemy tab @ left bottom .Put necessory ingrediants in alchemy inventory in the left (as said in magic book).
If you haven't learnt any alchemy recipe,find a alchemy trader (forgot his name , almost in the middle of Slavingrad,near market).Buy any scroll of recipe, right click on it,click 'learn'.Now it'll be in your magic book.Find ingredients as in it,